An electrodeless discharge lamp device for lighting an electrodeless discharge lamp having a bulb filled with a discharge gas is long-provided.
The electrodeless discharge lamp device comprises an electric power coupler. The electric power coupler is described as a coupler. The coupler is inserted into a cavity formed to a bulb filled with a discharge gas. FIG. 12 shows the coupler. As shown in FIG. 12, the coupler includes an induction coil (not shown) a pair of semi-cylindrical cores 1a, 1b (FIG. 12 shows the core 1b only), a thermal conductor 2, and a coil bobbin. The induction coil is configured to receive a high frequency electricity and then to generate a high frequency electromagnetic field for exciting the discharge gas. A pair of the cores 1a, 1b is arranged to form approximately cylindrical shape around which the induction coil is wound. The thermal conductor 2 is formed into a cylindrical shape and thermally coupled with the cores 1a, 1b. The thermal conductor 2 is for radiating heat generated at the cores. The coil bobbin is disposed between the cores 1a, 1b and the induction coil to intermediate between the cores 1a, 1b and the induction coil.
The cores 1a, 1b are made of a soft magnetic material having a good high frequency magnetic characteristic. The soft magnetic material is such as Mn—Zn ferrite. The cores 1a, 1b are respectively formed with an opening plane. The cores 1a, 1b are arranged to face each of the opening planes to form approximately cylindrical shape core as a whole.
The thermal conductor 2 is made of a material having a high thermal conductivity. The material having a high thermal conductivity is such as aluminum or copper, or alloy which is made of the aluminum and the copper. The thermal conductor 2 is inserted into a space formed between the cores 1a, 1b. The thermal conductor 2 shown in the FIG. 12 is integrally formed at its lower end with a base which is configured to support the thermal conductor. The base is formed at its circumference of a lower end with a flange 20. The thermal conductor 2 is configured to transfer the heat generated at the cores 1a, 1b to the flange 20 for radiating the heat from the flange 20 to an outside.
The coil bobbin 5 includes a winding body 50 and a pedestal 51. The winding body 50 is formed into a cylindrical shape having a small diameter, and is for covering the core 1 and the thermal conductor 2. The pedestal 51 is formed into a cylindrical shape having a large diameter, and is formed to attach the flange and to surround the base. A part of the winding body 50 which is configured to surround the circumference of the core 1 is formed around its circumference surface with the recess for winding the induction coil around.
The core 1 and the thermal conductor 2 is arranged to cooperatively form a space therebetween. The space is filled with an elastomeric resin such as a silicon rubber 4. The silicon rubber 4 is for adhering the core 1 and the thermal conductor 2, and is for thermally couples the core 1 with the thermal conductor 2. By this means the core 1 is prevented from excessive increasing of temperature of the core 1 by the silicon rubber 4 (for example, see Japanese Patent application no. H6-196006, paragraph [0008] to [0011], to [0020] and FIG. 1).
In addition, the above electrodeless discharge lamp is dimmed by applying a first high frequency electricity and a second high frequency electricity, alternately. The first high frequency electricity is set to have a frequency to light the electrodeless discharge lamp. The second high frequency electricity is set to have a frequency to light out the electrodeless discharge lamp. Furthermore, the first high frequency electricity is applied over a first period. The second high frequency electricity is applied over a second period. The electrodeless discharge lamp is operated by switching the first period and the second period, alternately. In this manner, the electrodeless discharge lamp is commonly dimmed (for example, see Japanese Patent application no. 2000-353600, paragraph [0005], [0014] to [0019] to [0020] and FIG. 1 to 4).
However, in the case that the above electrodeless discharge lamp is controlled by the above dimming control system with using the well known coupler at 50 percent dimming, the coupler generates noise rated at about 45 decibels at a location 20 centimeter away from the bulb. The above noise level generated from the coupler is unacceptable level in common lighting.
In the above dimming control system, voltage waveforms applied to the induction coil shows an abrupt increase in voltage such as surge which is generated at the time of switching the frequency for relighting the bulb. The abrupt increase in voltage causes vibrations of the core 1
In addition, as shown in FIG. 13, the elastomeric resin 4 is held at a space between the core 1 and the thermal conductor 2, thereby being pushed out from the space between the core 1a and core 1b. Therefore, center portions of an inside of the cores 1a, 1b directly come into contact with the thermal conductor 2. That is, the vibration of the core 1 is directly transferred to the thermal conductor 2. As a result, it is considered that the coupler causes an intense noise.